Biometric approach for authentication is appealing because of its convenience and possibility to offer security with non-repudiation. However, additional hardware, such as biometric scanners and complex software for feature extraction and biometric template matching, are required if biometric approach is to provide security for protecting sensitive data such as personal health information.
Cryptographic approach, on the other hand, ties data protection mathematically to the Key that is utilized to protect it. This allows a data owner to have complete control over one's personal information without relying on, or relinquishing control to, a third party authority. The protection of personal sensitive information is also not tied to complex software and hardware systems that may need constant patches to security holes.
Biometric authentication and authorization for data protection could be thought of as enabling security based on “what one is.” The lynchpin of biometric security is the use of sufficiently unique, but often imprecise, physiological or behavioral traits to characterize an individual for authentication and identification purposes. The characterization is expressed in form of some biometric signature, which often can be reduced to some feature vector or matrix representation. For example, a biometric face could be expressed in terms of a linearized vector of EigenMap or EigenFace components. The security parameter for assessing the strength of a biometrically based approach is typically related to the size of the underlying feature vector (or matrix) and the number of bits for representing a value, as well as the biometric data distribution leading to inter and intra variability—a main source of false negative or false positive alarms when applying biometric approach for security.
On the other hand, cryptographically based security could be thought of as a security approach based on “what one knows.” The lynchpin of cryptographic security is the secret key for decrypting a cipher text that is the encrypted form of the sensitive data. The security parameter for assessing the strength of a cryptographic approach is typically the key size in terms of the number of bits, and information leakage which can be measured by the information gain on the sensitive data given its corresponding cipher text and the mathematical structure of the cryptographic mechanism for encryption/decryption. In order to mitigate the risk of information leakage, semantic security is desirable.
In theory, the size of a biometric signature or the size of a secret key in cryptography could be increased indefinitely to increase the security strength. In practice, the limitation in the resolution of biometric sensors, among other factors, does not allow the security strength to be scaled proportionally. On the other hand, cryptographic approach has its own drawback too. Since the confidentiality of sensitive data is protected through encryption, one must keep the decryption key as a secret. Generally the secret key is generated and withheld by the party that handles the decryption of the sensitive data. If the secret key is compromised, the confidentiality of the sensitive data is compromised.
Therefore, an improved computational protocol which affords the advantages of both the cryptographic and biometric approaches is desired.